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This paper presents an electromagnetic-mechanical repair patch (EMRP) to restore the mechanical and electromagnetic (EM) wave absorption performance of a radar-absorbing structure (RAS) damaged by lightning strike. Several researchers have primarily focused on ensuring high repair efficiency, particularly in terms of the primary load-bearing properties of repaired fiber-reinforced plastics. However, no study has proposed a practical repair approach that considers the multi-functionality of the radar-absorbing structure. The EMRP method can be used to repair lightning strike damage in a radar-absorbing structure with electroless nickel-plated glass fabric, considering the need to maintain structural integrity and electrical continuity to achieve a high repair efficiency. Damage due to an artificial lightning strike was assessed in terms of area and depth of the damage using image processing, ultrasonic C-scan, and micro X-ray inspection. The EM characteristics of one-dimensional return loss scanning and the echo radar-cross-section level were measured to verify the stealth performance of the repaired radar absorber in the X-band. In addition, the tensile test results demonstrated that the repaired radar absorber had a high recovery rate of 93% compared to the pristine radar absorber. The experimental results obtained in this study validate the use of the proposed EMRP method in repairing radar-absorbing structures. [ABSTRACT FROM AUTHOR]

The joining of composite materials has traditionally been achieved by adhesive bonding or mechanical fastening. Mechanical fastenings require little or no surface preparation, and are easy to inspect for joint quality. However, they require machining of holes that interrupt the fiber continuity and may reduce the strength of the adherend. We proposed the new composite key joint to minimize the fiber discontinuity and strength degradation of adherend. Mechanical key joints with three different d/t (slot depth to thickness) ratios and two different e/w (edge length to width) ratios were manufactured and tested. Carbon-epoxy unidirectional prepreg (USN125) and plain weave prepreg (HPW193) were used for the composite key joints. Tensile tests were performed on the composite key joints and their failure modes were evaluated. Finite element analyses for the mechanical key joints were performed and the stresses around the key slot were calculated. From the tests, it could be concluded that the failure load of the key joints was about two times larger than those of a mechanical joint for the investigated composite joints. [ABSTRACT FROM PUBLISHER]